My 300GX is about 15 years old and a couple of the keys (E, F, F# in center of the keyboard) are sagging a bit, so I think I'll have to open it up and check for broken hammers. But the strange thing is that sometimes the E misbehaves! It will play the sound but does not sustain when held down (although it does sustain with the pedal). When I press it softly, it is somewhat ok, but when hit hard, it plays the initial impact sound then quickly dampens.

Not sure of what I'll find when I open it up but I suspect this has something to do with the rubber contact strip and the 2 contacts inside. Any ideas as to what could be causing this (and how to fix it)?
[attachment: roland rd-300gx keys.jpg]